Organothiol-containing siloxane resins as adhesion promoters for siloxane resins

ABSTRACT

A composition of matter which is an aqueous dispersion of an organothiolsilsesquioxane and colloidal silica is used as an adhesion additive for siloxane resins which have a low degree of substitution.

BACKGROUND OF THE INVENTION

This application is a continuation-in-part of application Ser. No.863,968 filed Dec. 23, 1977 now abandoned.

This invention is directed to the discovery that enhanced adhesion andshorter cure times can be achieved in certain siloxane resins which havea low degree of organic substitution.

Just recently, there was disclosed in U.S. Pat. No. 3,986,997, issuedOct. 19, 1976 to Harold A. Clark and assigned to the Dow CorningCorporation a new type of abrasion resistant coating composition whichconsists of a stable dispersion of colloidal silica and a siliconeresin. These coating compositions are unique because they are clearcoatings, have generally higher abrasion resistance than most organicmaterials used for the same purpose and are substantially easier toprepare and handle. These coatings are also easier to apply and for mostcoating purposes they adhere very well to the substrate they are appliedto.

There are other silicone resins which have been utilized to coat varioussubstrates for a variety of purposes and whenever there were desirableproperties of these resins that those skilled in the art wished toimpart to the substrate, there were always ways to gain the necessaryadhesion. For example, silicone resins are used on metal substrates forencapsulation purposes but some metals utilized in electrical systemssimply would not adhere to the silicone resins. Some of the commonapproaches to adhesion in these cases was to prime the metal surfacewith functional silanes such as ##STR1## or (CH₃ O)₃ SiCH₂ CH₂ CH₂ NHCH₂CH₂ NH₂, allowing an air dry and then applying the resin or, thesesilanes were added directly to the resin and then the resin was appliedto a cleaned metal substrate. Either way, the above noted silanes seemedto provide good adhesion, presumably due to their compatibility in (orwith) the silicone resins having a high degree of organic substitution.

When one scans the prior art surrounding the adhesion of silicone resinsto various substrates, one continuous thread winds its way through thepublications; there is no universal primer or adhesion additive andtherefore cautionary statements are always made in those publicationsthat the substrates and the adhesion promoters have to be matched forthe best results.

Thus it is not totally unexpected that the ordinary adhesion promotersdiscussed above would not function well with the siloxane resins havinga low degree of organic substitution.

Moreover, when the siloxane resins are being utilized as abrasionresistant coatings, the organosilanes discussed above are not normallyutilized because they tend to destroy the hardness of the coating andtherefore its effectiveness as an abrasion resistant coating. Onespecific example of a surface which does not readily adhere to thesiloxane resins having a low degree of substitution is polycarbonate.Polycarbonate tends to have inconsistent surface characteristics as itis formed into solid articles and therefore attempts to adhere siloxaneresins to such substrates have met with a great deal of difficulty.

What is needed therefore is a means to obtain consistent and uniformadhesion to troublesome substrates so that abrasion resistant siloxanecoatings having a low degree of substitution can be adhered to suchsubstrates.

THE INVENTION

The instant invention consists of a composition of matter which is apigment-free aqueous coating composition comprising a mixture of (A) adispersion of colloidal silica in lower aliphatic alcohol-water solutionof the partial condensate of a silanol of the formula RSi(OH)₃, or adispersion of colloidal silica in ether esters of ethylene of propyleneglycol-water solution of the partial condensate of a silanol of theformula RSi(OH)₃, in which R is selected from the group consisting ofalkyl radicals of 1 to 3 inclusive carbon atoms, the vinyl radical, the3,3,3-trifluoropropyl radical, the gamma-glycidoxypropyl radical, thegamma-methacryloxypropyl radical and the phenyl radical, at least 70weight percent of the silanol being CH₃ Si(OH)₃, said compositioncontaining 10 to 50 weight percent solids consisting essentially of 10to 70 weight percent colloidal silica and 30 to 90 weight percent of thepartial condensate, said composition containing sufficient acid toprovide a pH in the range of 2.5 to 6.0, having added thereto sufficient(B) to give 1-5 weight percent of the solids of (B) based on the weightof the total solids of (A) and (B) in the composition wherein (B) is anaqueous composition comprising a dispersion of colloidal silica in loweraliphatic alcohol-water solution of a partial condensate of a silanol ofthe formula R'Si(OH)₃, or a dispersion of colloidal silica in etheresters of ethylene or propylene glycol-water solution of a partialcondensate of a silanol of the formula R'Si(OH)₃ in which R' is selectedfrom HSR"-- and (HS)₂ R"-- wherein R" is selected from a groupconsisting of a divalent or trivalent aliphatic hydrocarbon radicalhaving 1-6 carbon atoms and phenylene the colloidal silica in (B) beingpresent in the amount of 34 to 50 weight percent and the amount of thepartial condensate of a silanol present in (B) being 50 to 66 weightpercent both based on the total weight of solids contained in (B), saidcomposition (B) containing 10 to 50 weight percent solids, saidcomposition (B) containing sufficient acid to provide a pH in the rangeof 2.8 to 5.2 until it is added to composition (A).

As will be evident to those skilled in the art, component (A) of theinventive composition is a known material and the preparation andhandling of such materials can be found in U.S. Pat. No. 3,986,997referred to above which patent is hereby incorporated by reference andforms part of this invention.

The second component (B) is the critical part of this invention. It isthis component, and the manner in which it is used with component (A),that gives the novelty to this invention.

Component (B) is an aqueous composition comprising either a dispersionof colloidal silica in lower aliphatic alcohol-water solution of apartial condensate of a silanol of the formula R'Si(OH)₃, or adispersion of colloidal silica in ether esters of ethylene or propyleneglycol-water solution of a partial condensate of a silanol of theformula R'Si(OH)₃ in which R' is selected from HSR"-- and (HS)₂ R"--wherein R" is selected from a group consisting of a divalent aliphatichydrocarbon radical having 1-6 carbon atoms and phenylene.

Component (B) is prepared essentially in the same manner as is component(A). The difference between the two materials is that the partialcondensate of (A) is primarily CH₃ Si(OH)₃ while the partial condensateof (B) is derived from a mercaptofunctional substituted silanol. Thus,the partial condensate of (B) is represented by the general formulaR'Si(OH)₃ in which R' represents (HS)₂ R"-- and HSR"--. R" in this caseis selected from divalent or trivalent aliphatic hydrocarbon radicals of1-6 carbon atoms and the phenylene radical.

Thus, R" can be, for example, ═CH--CH₂ CH₂, --CH₂ --, --CH₂ CH₂ CH₂ --,--(CH₂)₄, --CH₂)₆ or more specifically, ##STR2##

The partial condensate constitutes only a portion of the solids incomponent (B). The other essential ingredient is colloidal silica.

Just as in component (A) above, aqueous colloidal silica dispersionshaving a particle size in the range of 5-150 millimicrons in diameterare required. These silica dispersions are prepared by methodswell-known in the art and are commercially available under suchregistered trademarks as "Ludox" and "Nalcoag". It is preferred to usecolloidal silica of 10-30 mμ particle size. Colloidal silicas of thistype are relatively free of Na₂ O and other alkali metal oxides,generally containing less than 2 weight percent, preferably less than 1weight percent Na₂ O. They are available as both acidic and basichydrosols. Colloidal silica is distinguished from other waterdispersable forms of SiO₂, such as nonparticulate polysilicic acid oralkali metal silicate solutions, which are not operative in the practiceof the present invention.

The silica is dispersed in a solution of the siloxanol carried in alower aliphatic alcohol-water cosolvent or in an ether ester of ethyleneor propylene glycol-water cosolvent. Suitable lower aliphatic alcoholsinclude methanol, ethanol, isopropanol, and t-butyl alcohol. Mixtures ofsuch alcohols can be used. Isopropanol is the preferred alcohol and whenmixtures of alcohols are utilized it is preferred to utilize at least 50weight percent of isopropanol in the mixture to obtain optimum adhesionof the coating. The solvent system should contain from about 20 to 75weight percent alcohol to ensure solubility of the siloxanol. Suitableether esters of ethylene or propylene glycol are the well-known lowmolecular weight solvents such as carbitol acetate i.e. CH₃ COO(CH₂ CH₂O)₂ C₂ H₅, CH₃ COO(CH₂ CH₂ O)₂ C₄ H₉ and Cellosolve Acetate® i.e. CH₃COOCH₂ CH₂ OC₂ H₅ and such materials as CH₃ COOCH₂ CH₂ OCH₃ and CH₃COOCH₂ CH₂ OC₄ H₉ and analogs of such materials prepared from propyleneglycol. This solvent system should also contain from 20-75 weightpercent of the ether esters to ensure solubility of the siloxanol.Optionally one can utilize an additional water-miscible polar solvent,such as acetone, butyl cellosolve and the like in a minor amount, forexample no more than 20 weight percent of the cosolvent system.

To obtain optimum properties in the coating and to prevent immediategellation of the coating composition, sufficient acid to provide a pH of2.5 to 6.0 must be present. Suitable acids include both organic andinorganic acids such as hydrochloric, acetic, chloroacetic, citric,benzoic, dimethylmalonic, formic, glutaric, glycolic, maleic, malonic,toluene-sulfonic, oxalic and the like. The specific acid utilized has adirect effect on the rate of silanol condensation which in turndetermines shelf life of the composition. The stronger acids, such ashydrochloric and toluenesulfonic acid, give appreciably shortened shelfor bath life and require less aging to obtain the described solublepartial condensate. It is preferred to add sufficient water-misciblecarboxylic acid selected from the group consisting of acetic, formic,propionic and maleic acids to provide pH in the range of 4 to 5.5 in thecoating composition. In addition to providing good bath life, the alkalimetal salts of these acids are soluble, thus allowing the use of theseacids with silicas containing a substantial (greater than 0.2% Na₂ O)amount of alkali metal or metal oxide.

The composition (B) is easily prepared by adding the trialkoxysilane,such as R'Si(OCH₃)₃, to colloidal silica hydrosols and adjusting the pHto the desired level by addition of the organic acid. The acid can beadded to either the silane or the hydrosol prior to mixing the twocomponents provided that the mixing is done rapidly. The amount of acidnecessary to obtain the desired pH will depend on the alkali metalcontent of the silica but is usually less than one weight percent of thecomposition. Alcohol is generated by hydrolysis of the alkoxysubstituents of the silane, for example, hydrolysis of one mole of--Si(OC₂ H₅)₃ generates 3 moles of ethanol. Depending upon the percentsolids desired in the final composition, additional alcohol, water or awater-miscible solvent can be added. The composition should be wellmixed and allowed to age for a short period of time to ensure formationof the partial condensate. The composition thus obtained is a clear orslightly hazy low viscosity fluid which is stable for several days.

It is desirable to have in component (B) 34-50 weight percent ofcolloidal silica and 50-66 weight percent of the partial condensate ofR'Si(OH)₃, based on the weight of the colloidal silica and the partialcondensate of R'Si(OH)₃ in (B). Component (B) is used as a 10-50 weightpercent solids aqueous dispersion.

The coating composition formed by (A) and (B) is prepared by simplymixing components (A) and (B) together in such a ratio that there ispresent in the composition from 1-5 weight percent of the solids of (B)based on the weight of the solids in (A) and (B).

Buffered latent condensation catalysts can be added to the compositionso that milder curing conditions can be utilized to obtain the optimumabrasion resistance and abrasion in the final coating. Alkali metalsalts of carboxylic acids, such as potassium formate, are one class ofsuch latent catalysts. The amine carboxylates and quaternary ammoniumcarboxylates are another such class of latent catalysts. Of course thecatalysts must be soluble or at least miscible in the cosolvent system.The catalysts are latent to the extent that at room temperature they donot appreciably shorten the bath life of the composition, but uponheating the catalysts dissociates and generates a catalytic speciesactive to promote condensation. Buffered catalysts are used to avoideffects on the pH of the composition. Certain of the commerciallyavailable colloidal silica dispersions contain free alkali metal basewhich reacts with the organic acid during the adjustment of pH togenerate the carboxylate catalysts in situ. This is particularly truewhen starting with a hydrosol having a pH of 8 or 9. The compositionscan be catalyzed by addition of carboxylates such as dimethylamineacetate, ethanolamine acetate, dimethylaniline formate,tetraethylammonium benzoate, sodium acetate, sodium propionate, sodiumformate or benzyltrimethylammonium acetate. The amount of catalyst canbe varied depending upon the desired curing condition, but at about 1.5weight percent catalyst in the composition, the bath life is shortenedand optical properties of the coating may be impaired. It is preferredto utilize from about 0.05 to 1 weight percent of the catalyst.

To provide the greatest stability in the dispersion form while obtainingoptimum properties in the cured coating, it is preferred to utilize acoating composition having a pH in the range of 4-5 which contains 10-35weight percent solids; the silica portion having a particle size in therange of 5-30 millimicrons, the partial condensate from (A) and (B)being present in an amount in the range of 35 to 55 weight percent ofthe total solids in a cosolvent of methanol, isopropanol and water, thealcohols representing from 30 to 60 weight percent of the cosolvent anda catalyst selected from the group consisting of sodium acetate andbenzyltrimethylammonium acetate being present in an amount in the rangeof 0.05 to 0.5 weight percent of the composition. Such a composition isrelatively stable and, when coated onto a substrate, can be cured in arelatively short time at temperatures in the range of 75°-125° C. toprovide a transparent abrasion resistant adherent surface coating.

The coating compositions of the invention can be applied to solidsubstrates by conventional methods, such as flowing, spraying or dippingto form a continuous surface film. Although substrates of soft plasticsheet material show the greatest improvement upon application of thecoating, the composition can be applied to other substrates, such aswood, metal, printed surfaces, leather, glass, ceramics and textiles.The compositions are especially useful as coatings for dimensionallystable synthetic organic polymeric substrates in sheet or film form,such as acrylic polymers, for example poly(methylmethacrylate),polyesters, for example poly(ethyleneterephthalate) and polycarbonates,such as poly(diphenylolpropane)carbonate and poly(diethylene glycol bisallyl)carbonate, polyamides, polyimides, copolymers ofacrylonitrile-styrene, styrene-acrylonitrile-butadiene copolymers,polyvinyl chloride, butyrates, polyethylene and the like. Transparentpolymeric materials coated with these compositions are useful as flat orcurved enclosures, such as windows, skylights and windshields,especially for transportation equipment. Plastic lenses, such as acrylicor polycarbonate ophthalmic lenses, can be coated with the compositionsof the invention. In certain applications requiring high opticalresolution, it may be desirable to filter the coating composition priorto applying it to the substrate. In other applications, such ascorrosion-resistant coatings on metals, the slight haziness (less than5%) obtained by the use of certain formulations, such as thosecontaining citric acid and sodium citrate, is not detrimental andfiltration is not necessary.

By choice of proper formulation, including solvent, applicationconditions and pretreatment of the substrate, the coatings can beadhered to substantially all solid surfaces. A hard solvent-resistantsurface coating is obtained by removal of the solvent and volatilematerials. The composition will air dry to a tack-free condition, butheating in the range of 50° to 150° C. is necessary to obtaincondensation of residual silanols in the partial condensate. This finalcure results in the formation of silsesquioxanes of the formulaRSiO_(3/2) and R'SiO_(3/2) and greatly enhance the abrasion resistanceand adhesion of the coating. The coating thickness can be varied bymeans of the particular application technique, but coatings of about 0.5to 20 micron preferably 2-10 micron thickness are generally utilized.Especially thin coatings can be obtained by spin coating.

Now, the following examples are offered so that those skilled in the artcan better understand and appreciate this invention.

EXAMPLE 1--Preparation of Component (A)

A mixture of 10.5 grams of glacial acetic acid and 304.5 grams ofmethyltrimethoxysilane was slowly added to 444.1 grams of a commerciallyavailable aqueous dispersion of colloidal silica having an initial pH of3.1 containing approximately 34% SiO₂ of approximately 22 millimicronparticle size and having an Na₂ O content of less than 0.01 weightpercent. The acidified dispersion was stirred while it was slightlycooled by an external ice bath to keep the temperature below about 10°C. The dispersion was stirred for about 1 hour beyond the end of thefull addition of the silane while generating methanol andmethyltrisilanol. Upon standing for a while, the pH stabilized at 4.5and the material was stripped to approximately 60 percent solids anddiluted to 35 percent solids using alcohol.

EXAMPLE 2--Preparation of Component (B) (50 weight percent HSCH₂ CH₂ CH₂Si(OH)₃ and 50 weight percent SiO₂)

A solution (142.9 grams) of 48.6 grams of the same colloidal silica aswas used in Example 1, 94.3 grams of water and 10 grams of glacialacetic acid was placed in a glass reaction flask and there was addedthereto 77.2 grams of mercaptopropyltrimethoxysilane with moderatestirring to produce a hydrolyzate containing HSCH₂ CH₂ CH₂ Si(OH)₃.134.6 grams of isopropanol was added, the mixture stirred and thenstripped to 48.2% solids and then rediluted with alcohol to 35 percentsolids.

EXAMPLE 3--Component (A) from Example 1 was further diluted to 22.5weight percent solids using alcohol

Various quantities of component (B) were then added to component (A) soas to give 5 weight percent of the solids of component (B) based on thetotal solids content of (A) and (B), in the coating composition.

In the following data where Δ haze values appear, it can be assumed thatthe adhesion of the coating in that example is 100% as measured by the1/8" crosshatch tape pull test.

The data was gathered on clear Lexan polycarbonate panels manufacturedby the General Electric Plastics Division, Pittsfield, MA.

Prior to coating the test panels were cleaned in the following manner.The panels were washed with isopropanol and then hexane and then rubbedgently with a dust free cloth containing heptane. The panels were thenrinsed with isopropanol, air dryed and heated at 125° C. for 2 hours,allowed to cool to room temperature and then coated immediately.

The panels measured 4"×4"×1/8" thick and were flow coated with thematerial from Example 2 at 22.5 weight percent solids to give a thincoating of 3 microns thickness.

The abrasion resistance was measured according to ASTM Method D1044-56using a 500 gm test load and CS-10F abrasive wheel for 500 resolutions.The percent change in haze from an unabraded surface to an abradedsurface is reported. Haze is defined as that percentage of transmittedlight which in passing through the specimen deviates from the incidentbeam by forward scattering according to ASTM Method D1003-61. A HunterHaze Meter, Gardner Laboratory, Inc. was used.

To determine haze, the amount of diffused light is measured, divided bythe amount of transmitted light and multiplied by 100. NA indicates noadhesion. Results:

    ______________________________________                                                    5% Additive Level                                                             Relative Humidity 65%/Cure 125° C.                         Cure Time   Air dry time after coating - hours                                hours       1/2        11/2       3                                           ______________________________________                                         1/2        NA         NA         NA                                          11/2        0.7%       1.0%       3.0%                                        3           1.5%       2.5%       2.8%                                        ______________________________________                                    

    ______________________________________                                                    0% Additive Level*                                                            Relative Humidity 65%/Cure 125° C.                         Cure Time   Air dry time after coating - hours                                hours       1/2        11/2       3                                           ______________________________________                                         1/2        NA         NA         NA                                          11/2        NA         NA         NA                                          3           NA         NA         NA                                          ______________________________________                                         *0% additive level in component (A) without component (B).               

    ______________________________________                                                    5% Additive Level                                                             Relative Humidity 35%/Cure 125° C.                         Cure Time   Air dry time after coating - hours                                hours       1/2        11/2       3                                           ______________________________________                                         1/2        NA         NA         0.8%                                        11/2        0.4%       1.0%       1.6%                                        3           1.5%       1.2%       --                                          ______________________________________                                    

    ______________________________________                                                    0% Additive Level                                                             Relative Humidity 35%/Cure 125° C.                         Cure Time   Air dry time after coating - hours                                hours       1/2        11/2       3                                           ______________________________________                                         1/2        NA         NA         NA                                          11/2        NA         NA         NA                                          3           NA         NA         NA                                          ______________________________________                                    

This data shows that enhanced adhesiveness is obtained by the use ofthis invention and that the incorporation of the component (B) incomponent (A) shortens the cure time of component (A).

EXAMPLE 4

Further abrasion tests were run on the above coating composition to showthat the addition of component (B) to component (A) did notsignificantly detract from the abrasion resistant qualities and that theabrasion resistance on the inventive composition is more prolonged thancomponent (A) without component (B).

Cured (X) hours at 125° C.

% Δ Haze

    ______________________________________                                        #        1%          1%          0%                                           Cycles   HS/16 hr.   HS/5 hr.    HS/5 hr.                                     ______________________________________                                         500     0.9         1.2         1.4                                          1000     2.2         2.0         2.9                                          1500     2.6         3.0         5.1                                          2000     3.2         4.7         6.5                                          2500     3.5                                                                  3000     4.5                                                                  ______________________________________                                    

Note that the additive level is 1% and not 5% as in the previousexample. Note also that this data was generated on panels which werehandled and coated the same as in the previous example.

EXAMPLE 5

This example illustrates the use of ether esters of ethylene, and water,as a co-solvent.

Methyltrimethoxysilane, 214 gms. was slowly added to a mixture of 309gms. of the same type of colloidal silica as was used in Example 1 and10.5 gms. of glacial acetic acid at a temperature of about 8° C. Themixture was stirred and cooled to maintain the temperature at about 8°C. The reaction mass was then stripped under vacuum to remove somevolatiles until there remained 430 gms. of material. This hydrolyzate,215 gms. at 46.6% solids was then treated with 7.5 gms. ofmercaptopropyltrimethoxysilane and 195 gms. of cellosolve acetate. Thematerial at this point was stirred to make homogeneous and clear. Itcontained about 35 weight percent solids. The coating when cured gave aclear coating having a pencil hardness of 6H.

That which is claimed is:
 1. A composition of matter which is apigment-free aqueous coating composition comprising a mixture of (A) adispersion of colloidal silica in lower aliphatic alcohol-water solutionof the partial condensate consisting essentially of of a silanol of theformula RSi(OH)₃ or a dispersion of colloidal silica in ether esters ofethylene or propylene glycol-water solution, of the partial condensateconsisting essentially of of a silanol of the formula RSi(OH)₃ in whichR is selected from the group consisting of alkyl radicals of 1 to 3inclusive carbon atoms, the vinyl radical, the 3,3,3-trifluoropropylradical, the gamma-glycidoxypropyl radical, the gamma-methacryloxypropylradical and the phenyl radical, at least 70 weight percent of thesilanol being CH₃ Si(OH)₃, said composition containing 10 to 50 weightpercent solids consisting essentially of 10 to 70 weight percentcolloidal silica and 30 to 90 weight percent of the partial condensate,said composition containing sufficient acid to provide a pH in the rangeof 2.5 to 6.0, having added thereto sufficient (B) to give 1-5 weightpercent of the solids of (B) based on the weight of the total solids of(A) and (B) in the composition wherein (B) is an aqueous compositioncomprising a dispersion of colloidal silica in lower aliphaticalcohol-water solution of a partial condensate of a silanol of theformula R'Si(OH)₃ or a dispersion of colloidal silica in ether esters ofethylene or propylene glycol-water solution of a partial condensate of asilanol of the formula R'Si(OH)₃ in which R' is selected from HSR"-- and(HS)₂ R"-- wherein R" is selected from a group consisting of a divalentor trivalent aliphatic hydrocarbon radical having 1-6 carbon atoms andphenylene, the colloidal silica in (B) being present in the amount of 34to 50 weight percent and the amount of R'Si(OH)₃ present in (B) being 50to 66 weight percent both being based on the total weight of solidscontained in (B), said composition (B) containing 10 to 50 weightpercent solids, said composition (B) containing sufficient acid toprovide a pH in the range of 2.8 to 5.2 until it is added to composition(A).
 2. A coating composition in accordance with claim 1 in which thealcohol or ether ester in the solution is present in an amount in therange of 20 to 75 weight percent based on the total weight of thesolution.
 3. A composition in accordance with claim 2 wherein at least50 weight percent of the alcohol is isopropanol.
 4. A composition inaccordance with claim 2 wherein the solution contains a water-misciblepolar solvent in an amount up to 20 weight percent based on the weightof suspending medium.
 5. A composition in accordance with claim 2wherein at least 50 weight percent of the ether ester is CH₃ COOCH₂ CH₂OC₂ H₅.
 6. A composition in accordance with claim 2 wherein the acid iswater-miscible organic acid selected from the group consisting of aceticacid, formic acid, propanoic acid and maleic acid.
 7. A composition inaccordance with claim 6 containing from about 0.05 to 1.5 weight percentof a buffered latent silanol condensation catalyst.
 8. A composition inaccordance with claim 7 containing a sodium catalyst as the sodium saltof the water-miscible organic acid.
 9. A composition in accordance withclaim 7 containing as the catalyst a carboxylic acid salt of an amine.10. A composition in accordance with claim 7 containing as the catalysta quaternary ammonium salt.
 11. A composition in accordance with claim10 wherein the salt is benzyltrimethyl ammonium acetate.
 12. Acomposition in accordance with claim 11 wherein the partial condensateRSi(OH)₃ is present in an amount in the range of from 40 to 60 weightpercent of the total solids.
 13. A composition in accordance with claim12 wherein R'Si(OH)₃ is HSCH₂ CH₂ CH₂ Si(OH)₃.